Method of making gold filled stock



Nov. 27,1945. T. c. JARRETT 23,89,981

METHOD OF MAKING GOLD FILLED STOCK Original Filed Feb. 8, 1941 I I l 1 l IN VEN TOR TRHC Y C- \JHRRET'T' Patented Nov. 27, 1945 METHOD OF MAKING GOLD FILLED STOCK Tracy C. Jarrett, Catonsville, Md, assignor to American Optical Company,

Southbridge,

Mass, a voluntary association of Massachusetts Original application February 8, 1941, Serial No. 378,111. Divided and this application July 20, 1942, Serial No. 451,639

4 Claims.

This invention pertains to a method of pro ducing what is commonly referred to as goldfilled bar stock, and more particularly to the manufacture of gold-filled bar stock utilizing powdered metals as a core in lieu of a solid core.

This application is a division of my co-pendin application Serial No. 378,111, filed February 8, 1941, Patent No. 2,365,083.

It is a primary object of this invention to provide methods for producing gold-filled bar stock for utilization of a powdered metal core.

A further object of the invention is to use a powdered core with an outer metallic shell comprising an assembly having a lower specific gravity than a substantially similar assembly made using a solid core with the same outer shell covering.

A still further object is to utilize a shell of gold or other metal having the shell of metal used in conjunction with a filler of powdered metals with one of the metals in the powdered filler hav ing a lower melting point than the major portion of the metals, 2. function of the metal having the lower melting point will be to act as a bond.

A still further object of the invention is to utilize a shell of material having. a filter of powdered metal with one of the metals in the powdered filler having a lower melting point than the major portion of metals comprising the powdered filler and thereafter heating or sintering at proper temperatures to obtain adequate bonding of the major portion of the particles comprising the powdered metal filler.

A still further object of the invention is to produce gold-filled bar stock material to be reduced by any suitable means into gold-filled wire wherein the metallic shell is filled with powdered metal or metals and compressed and thereafter sintered to form a metal object having a lower density than it would have if made using a solid core or the same material.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing, and it will be apparent that many changes may be made in the details of construction, arrangement of parts, and steps in the process without departing from the spirit of the invention as expressed in the accompanying claims. The exact details shown and described are preferred forms only shown by way of illustration and are not to be considered as limitations.

Referring to the drawing:

Fig. 1 is a side view of a bar of gold-filled metal ready for the elongation process.

Fig. 2 is a sectional view taken along lines 2-2 of Fig. 1 indicating that the core material consists of powdered metals.

Fig. 3 is a sectional view of the compression operation wherein the shell of metal has compressed therewithin the powdered metals.

Heretofore, the gold-filled bar stock was made by utilizing a core of solid material which had a shell of precious metal such as gold compressed about the skin of the core material to obtain a specific quality of gold. It was necessary to have the shell of gold at a certain thickness relative to the specific gravity or density of the core material.

The present invention contemplates the use of a comparatively thin shell of gold having a powdered metallic filler so that the specific gravity of the entire unit or assembly may be reduced so that the quality of the gold-filled resulting bar stock will be the same as the former method of using the solid metallic core based on the density of the various metals.

Referring to the drawing and more particularly to Fig. 1, 4 is the assembly having the shell of metal 5.cy1indrically encasing a core of powdered metal which metal may be of any constituency depending upon the desired specific gravity of the assembly or completed bar stock and the quality of the core material after the sintering operation.

The cross sectional view shown in Fig. 2 shows the assembly 4 with the shell of metal 5 encasing the powdered metal 6. This view is purely symbolical and represents generally that powdered metals are used for a filler of metallic shell.

The view shown in Fig. 3 represents the compression operation wherein a die I having orifice 8 therein is used as aholding member to prevent the shell from expanding during the compression operation. The die is made of any suitable material such as steel. A base plate 9 is placed below the die I and has an orifice therein axially aligned with the orifice 8 of the die and being substantially of similar diameter as the die orifice 8.

Compression plungers II! are adapted to be inserted into the orifice 8 of the die 1 and having the greatest diameter of the plunger appreciably smaller than the internal diameter of the orifice 8 in the die 7. A knockout plunger II is shown in intimate engagement with the base plate 9 with the upper portion of the knockout plunger extending into the orifice 8 of the die 1. The

lower compression plunger has substantially the same dimensions as the upper compression plunger with the shaft of the lower compression plunger having a working fit with the inside hole of the knockout plunger. The metallic shell 5 is shown engaging the side-walls of the die 1 while the metallic particles or metallic filler 6 as shown within the confines of the shell 5 by the compression plungers II].

In operation, the metallic shell 5 is filled with the powdered metals in any suitable manner. One way of performing this operation is to have the shell of metal inserted within the die having the bottom closure thereof engaged by the lower plunger In so as to restrict any of the particles from passing between the plunger head and the inside skin of the metallic shell *5 when the compression operation is in progress. After the metallic shell is suitably filled with the powdered metal, power is applied to the plunger In in sufficient force to compress the particles to the desired pressure. After the compression operation is attained, the plungers are removed and an upward force exerted on the knockout plunger 1 I to force the assembly 5 out of the die I.

After the knockout operation, the entire assembly is heated to a temperature sufiicient to cause adequate bonding between the particles of the powdered metal and the powdered metal particles and the metallic shell.

The major purpose of the invention, as set out hereinbefore, is to produce a gold-filled wire lighter than the present gold-filled wire commercially manufactured, and also to cut down the amount of gold actually used in the shell as compared with the shell used for making gold-filled wires having a solid core of such metals as nickel, nickel alloy, beryllium-copper or the like. If the same shell, having the same thickness, were employed in making powdered metal gold-filled wire, in lieu of the solid core gold-filled wire, higher quality product would result. To produce a gold-filled shell using powdered metals having the same quality as the present gold-filled wire employing a solid core, the shell may be made considerably thinner so that the density of the powdered goldfilled wire would be approximately to less than a product resulting from gold-filled wire having a solid nickel core such as used commercially today.

To make the powdered metal filler for powdered metal gold-filled wire it is possible to use a pure metal such as copper, nickel or an alloy consisting of copper, nickel, cobalt, berylliumcopper and such elements as found to be used satisfactorily in the optical trade as a coin metal as a base in the making of the gold-filled wire. These compositions of the alloys may have wide limits, ranging from the pure metals themselves to various proportions of the combinations of one or more metals. The powdered metals are thoroughly mixed if an alloy is used, and then compressed in a suitable disk by means of pressure inside of the gold shell which is to be the permanent'container of the gold-filled product. This powder, after compressing in combination with or-without a silver bond, is then sintered at a proper temperature suitable for sintering and alloying the shell with the combination of powdered metals to form a solid mass of powdered goldfilled wire. The temperature will vary with the composition of the mixture of the powdered metals to be used as the so-called core for the gold-filled wire.

The temperature must be controlled in all cases,

depending upon the composition, soas to bring about a, bond between the particles of the metal themselves and join themselves in turn to the inside of the gold shell by means of an alloying action or diffusion. The inside of the shell before filling with the powders must be properly prepared andhave a chemically clean surface. This surface may or may not be coated with another metal, such as by electroplating, so as to accelerate the action of the bonding of the sintered particles of the powdered core to the gold shell itself. Suitable metals for plating the inside of the shell might be silver, gold, nickel, copper or tin. These metals will be applied depending upon the diffusion required and a mixture of the core to be forced into the shell. The sintering is performed in a suitable atmosphere after the pressure has been applied to the mixture of the metals. This suitable atmosphere may be any atmosphere that is reducing and not oxidizing.

The temperature range varies from approximately 120051 to 1600 F. depending upon the perature is obtained for the sintering operation,

In all cases the sintering temperature must be below the softening point of the metallic shell, such as a solid gold shell usedras the .outer covering for gold-filled bar stock.

This process is not limited to a solid gold shell but may be used on any metal or alloy of metals which will diffuse and bond itself to the compressed mixture of powdered metals. In no case should the sintering temperature go beyond the softening point of the shell used. The sintering temperature can not be above the melting point of the highest melting point of the powdered metal used excluding the melting point of the bonding powdered metals. Some of the low melting metals used in the mixture may exceed the melting point but they merely act as a bonding material and alloy with the higher metalsused and. would be used in smaller percentages than the parent powdered metal.

Having described my invention, I claim:

1. Themethod of forming precious metal fille'l stock of a given size and quality having a specific gravity which is less than precious metal filled stock of a similar nature, size and quality formed with a solid core comprising forming a tubular precious metal shell to a given size and with the side Walls thereof of a controlled substantially uniform thickness, supporting said shell in a confining die, placing metallic particles of desired base metals in said shell with said particles comprising in part a metalhaving a lower melting point than the major portion of the metallic particles, subjecting said particles to a compression force of an amount sufficient to position said particles in intimate relation with each other and with the inner walls of the shell and subjecting said shell and compressed particles of metal to heat of a temperature sufficient to bring about a sintering of said particles with each other and with the inner walls of the shell, with the upper limit of said temperature being below the melting point of the particles of highest melting point and with said melting point being below the melting point of the shell, the predetermined size of the stock being held substantially constant throughout the different operations.

2. The method of forming gold filled stock of a given size and quality having a specific gravity which is less than gold filled stock of a similar nature, size and quality formed with a solid core comprising forming a tubular gold shell to a given size and with the side walls thereof of a controlled substantially uniform thickness, supporting said shell in a confining die, placing metallic particles of desired base metals in said shell with said particles comprising in part a metal having a lower melting point that the major portion of the metallic particles, subjecting said particles to a compression force of an amount sufficient to position said particles in intimate relation with each other and with the inner walls of the shell and subjecting said shell and compressed particles of metal to heat of a temperature sufiicient to bring about a sintering of said 7, particles with each other and with the inner walls of the shell, with the upper limit of said temperature being below the melting point of the particles of highest melting point and with said melting point being below the melting point of the shell, the predetermined size of the stock being held substantially constant throughout the diiferent operations.

3. The method of forming gold filled stock of a given size and quality having a specific gravity which is less than gold filled stock of a similar nature, size and quality formed with a solid core comprising forming a tubular gold shell to a given size and with the side walls thereof of a controlled substantially uniform thickness, supporting said shell in a confining die, placing metallic particles of a coin metal selected from a group comprising copper, nickel or alloys consisting of copper, nickel, cobalt and berylliumcopper in said shell with said particles comprising in part a metal having a lower melting point than the major portion of the metallic particles, subjecting said particles to a compression force of an amount sufiicient to position said particles in intimate relation with each other and with the inner walls of the shell and subjecting said shell and compressed particles of metal to heat of a temperature suflicient to bring about a sintering of said particles with each other and with the inner walls of the shell, with the upper limit of said temperature being below the melting point of the particles of highest melting point and with said melting point being below the melting point of the shell, the predetermined size of the stock being held substantially constant throughout the difierent operations.

4. The method of forming precious metal filled stock of a given size and quality having a specific gravity which is less than precious filled stock of a similar nature, size and quality formed with a solid core, the steps of forming a tubular shell of precious metal to a given size and with the side Walls thereof of a controlled substantially uniform thickness, supporting said shell in a confining die shaped substantially to the outer shape of the shell, placing metallic particles of a desired base metal in said shell with said particles having a. lower melting point than the metal of the shell, subjecting said particles to a compression force of an amount suflicient to position said particles in intimate relation with each other and with the inner walls of the shell and subjecting said shell and compressed particles of metal to heat of an amount sufficient and controlled according to said metals so as to bring about a sintering of said particles with each other and to bond said particles with the inner walls of the shell, the thickness of the side walls of the preciOus metal tubular member being controlled according to the amount of base metal used so as to obtain a desired specific gravity, the predetermined size of the stock being held substantially constant throughout the difierent operations.

TRACY C. JARRETT. 

